Single-beam color television picture tube



June 26, 1962 Filed Sept. 17, 1959 w. VElTH 3,0415489 SINGLE-BEAM COLORTLEVISION PICTURE TUBE 3 Sheets-Sheet l -J me 26, 1962 w. VElTH 3,o4;489

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United States Patent O 3,041,489 SINGLE-BEAM COLOR TELEVISION PICTURETUBE Werner Veitl, Munich, Germany, assignoto Siemens und HalskeAktiengesellschai't Berlin and Munich, a`

corporation of Germany Filed Sept. 17, 1959, Ser. No. %40,706 Claimspriority, application Germany Sept. 26, 1958 12 Claims; (Cl. 313-68) ascreen to produce a color picture.- The common feature of these tubesresides in the utilization of a picture screen upon which are provided,in discrete regularly disposed planes, two or more luminescentsubstances which become luminous in different colors responsive toelectron impact. Electron beam tubes of this type make it possible toexcite the diflerent color planes on the'picture screen eachindependently of the others. The structures of these tubes difierconsider-ably and are in part quite complicated. However, the mostdifiicult problem in the Construction of such color picture tubesresides in the accuracy with which the individual color points belongingto one picture point are over the entire picture plane struck -by therespectively associated 'electron beams.

A tube of this type exhibiting great striking certanty is, for example,the shadow m-ask tube Operating with three separate electron beams, eachof which can be modulated with respect to its intensity. The so-calledmasking electrode of such a tube contains a great number of holes-whichhave respectively allocated thereto, upon the picture screen, a group ofvery small and usually circular surfaces, such surfaces corresponding tothe basic colors and being respectively struck at difierent angles ofincidence by the electron beams projected through the respective holes.

While this known tube permits simultaneous recording of the three basiccolors, endeavors -were made for a long time to avoid complicationsattending in such tube the correct focusing and clearcut determinationof an intersection point of the three beams.

It has therefore been suggested to use Variously designed tubesemploying, as contrasted withvthe indicated color picture tube, only oneelectron beam which is modulated so that it produces the. three basiccolors, blue, red, green, stagewise, that is, successively.

`In connection with one of these known tubes, there is provided a gridsystem-ahead of the picture screen, through which the electron beam isat difierent instances directed upon difierent color surfaces,especial1y color strips. The color selection grid consists of two parts,such that each one of a plurality of wires extending in parallel in oneplane is connected to each side always with the second next wire andthat correspondingly modulated color selection voltage is connectedbetween directly adjacent wires.

In connection with another known color picture tube, the luminescentscreen consists of regularly disposed color strips which are combined ingroups in accordance with the three basic colors, a secondary emissionstrip being inserted between each two of such color strips.

r The deflection velocty of the beam is by means of an auxiliary pilotbeam, based upon released secondary electrons, so adjusted, by a verycomplicated procedure and by way of a correspondingly involved amplifierrequiring ice about forty tubes, that the correct color is in -anyinstant struck by the beam.

The problem underlying the invention is to provide a color picture tubeof simple -construction, Operating with only one electron beam, whereinthe desired colors for each individual picture point are struck withabsolute certainty over the entire picture by producing, within therange of a particular control device serving the color selection, at thebeginning of -a strong acceleration field, electrons which are easilycontrolled for the purpose in view, that is, relatively slow electrons,while the requirements placed on the deflection elements correspondsubstantially to those which are posed in the case of simple picturetubes (monochrome tubes) or in the case of oscillograph tubes. The colorpicture tube shall inter alia also satisfy the requirements of theso-called National Television System Committee, hereinafter referred toas--the NTSC method, and shall also be directly applicable, that is,without changing the modulation voltage on the color selection grid, forthe reproduction of monochrome pictures.

This object is in accordanoe with the invention achieved by providing acolor television picture tube having focusing and deflection meanscustomary in the case of monochrorne picture tubes and, among others,having disposed in the evacuated tube stern a system for producing anelectron beam which is controllable (which can be modulated) withrespect to its intensity, and having a picture screen to which is'applied a high voltage and provided with at least two regularlydiscretely distributed surfaces (strips) of luminescent substances whichbecome luminous in -difierent colors responsive to electron impact andform an elementary group, and having moreover at least one grid disposedahead of the picture screen spaced there'om and extending practicallyparallel thereto, by making the grid, in the manner of a Venetianblini-of narrow metallic slats', the width and doubled mutual spacingamounting at the most to one and one-half of the picture point width,mutually corresponding positions of neighboring individual elementsbeing mutually spaced from one another approximately corresponding tothe single picture point width or less, by pl-acing the metal slats atan incline to the tube axis, such that, as in the case of a partiallyopen Venetian blind, the view in the direction of the tube aXis ispractically closed, easily influenced slow electrons emerging within therange of the grid (gaps between the metal slats), such electrons beingon the screen side by the acceleration field of the screen electrodedeflected in their paths and thereby ocused in such a way that they are,by further means for periodically affecting their acceleration (colorselection means), successively pictured upon the individual color stripsof an elementary group of the screen allotted respectively to a gap-formed by two adjacent metal slats.

It is essential tor the invention that the electrons emerging from thegrid arrangement under the influence of the strong pulling field of thescreen (screen electrode) are defiected and thereby particularly`aceurately focused upon the screen, and, moreover, that all electronshave substantially identical velocity, so as to `obtain good conu'astaction in addition to good striking certainty.

The various objects and features of the invention will appear from thedescription of embodiments which will be rendered 'below with referenceto the accompanying drawings which are more or less schematical andlimited to essentials, omitting parts known from normal picture tubesorleaving such parts unreferenced. In the drawings,

FIG. l shows a color picture tube according to the invention, alsoindicating the course of the electron beam;

FIGS. 2 to 4 show the grid arrangement and respectively indicate thebeam course at different breke or suppression conditions; FIG. 3 howevershowing, as contrasted with the other figures, an example of anarraigement without auxiliary color selection grid, namely, anarrangement in which the color selection voltage is placed on the screenelectrode.

FIG. illustrates circuit features and indicates typical voltageconditions to give an example; and

FIG. 6 shows a grid arrangement similar to the one represented in FIG. 3but employing a particular screen electrode.

In FIGS. l and 5, numeral 1 indicates the tube envelope and numeral 2the course of the electron beam. The electron beam is in usual mannerproduced in a generating system 3, comprising a cathode, a controlelectrode (Wehnelt cylinder) and an acceleration electrode, the beambeing accelerated and focused by suitable means. The electron beam is,for example, 'by means of a magnetic deflecton device disposed as shownat the transition from the stern to the cone part of the tube, initiallydeflected so that it describes a rectangular raster in a planeapproximately in parallel to the tube base; However, the electron beamis, by means of a cylindrical electrode 4, cooperatin'g with theacceleration anode of the beam generating system, decelerated or sloweddown, focused and defiected in a direction parallel to the tube axis, sothat it enters approximately perpendicularly into the plane of the grid5, disposed in back of the cylindrical electrode 4 and fashioned in themanner of a Venetian blind. In back of this Venetian blind grid is acolor selection grid 6 consisting of tensioned wires disposed inParallel in a common plane, and spaced therefrom is the luminescentscreen 7 backed by a conductive support 8. A high voltage is applied tothe support 8 and thus, in efi'ect, to the screen 7, so as to acceleratethe electrons leaving the Venetian blind grid with slow initialVelocity, to the required terminal energy. i

A suitable color selection which is in the described embodimentettected, inter alia, by the grid 6, shall be explained more in detailwith the aid of the part of the grid arrangement illustrated in FIG. 2.For this embodiment, the voltage, produced by the potential of theVenetian blind grid 5, is selected with reference to the cathode, sothat the electrons of the beam 2 strike With a velocity corresponding toa voltage of 500-1000 v., for the purpose of effecting on the Venetianblind grid 5, serving in this case as a target, a maximum secondaryemission. The metal slats of the Venetian blind grid serving as impactelements, which are inclined at about 45 to the tube axs, are of a widthand are mutually spaced so that they prevent passage of directelectrons. This requirement is, for example, at a 45 inclinationsatisfied with a width of the metal slats arnounting to approximatelyone and one half of the distance of corresponding points, for example,the edges of two adjacent slats. In the drawing, this dimension is equalto the spacing between the two marginal rays indicated by numeral 2,that is, equal to the width of the picture points. An upper limit forthe width of the impact or target slats, which is technically stilleasily attained is, for example, on the order of 0.8

millimeter, assnming thereby a 600 line picture of a size of about 30centimeters by 40 centimeters and an electron beam diameter of about 0.5millimeter. In order to obtain a good secondary emission yield andtherewith good tube economy, the impact slats shall be made of arnaten'al suitable for secondary emission or shall be correspondinglyactivated in known manner.

The secondary electrons released at the impact slats are by theelectr-ical field between the Venetian blind grid and the screenelectrode 7 or the associated support 8, which is as indicated in FIG. 5at high voltage, along their paths 9 strongly deflected toward thescreen, and thereby focused, and are by the auxiliary influence of thecolor selection grid 6, pictured, for example, in the color red, upon acolor strip of the screen 7, which extends perpendicularly to the planeof the drawing. Thedeflection ettect of the permeating electrical fieldis changed and the secondary electrons are focused upon the desiredcolor strip according to this voltage, by changing the color selectionvoltage on the color selection grid 6, the respective wires of which arespaced from the edges of the Venetian blind grid elements facing towardthe screen. Moreover, since the so-called color selection grid disposedbetween the Venetian blind grid and the screen electrode controls thenumber of electrons passing through, analogous to the control grid of atriode, it is possible to improve the economy of the tube byadvantageously arranging the color strips in their sequence, forexample, so that the one with the least illumination yield is struck bythe strongest electron beam, and eitecting for the color selectionvoltage a corresponding phase Shift.

The color selection can also be obtained, instead of by the explainedgrid control, in particularly advantageous manner by a control with thescreen electrode or its acceleration voltage, respectively. FIG. 3 showsparts of the electrode an'angement and the beam course for acorresponding embodiment.

Referring to FIG. 3, the secondary electrons released by the action ofprimary beam 2, with lower voltage of the screen electrode 8, -arefocused to strike the color strip arranged at the left and designated byR while at a higher voltage are focused to strike the color stripfurther to the right and designated by B. Such a color selection can beobtained by superimposing, for example, upon a basic high voltage forthe screen electrode, a high frequency color selection voltage (MS inFIG. 5, connected to the color selection grid 6) which is periodicallyvaried in three stages. It is in connection with this kind of colorselection likewise possible to provide in advantageous manner for thedifferent illumination yield of the individual colors by energizing theless sensitive color with a secondary electron beam of higher impact orstriking energy, etc., using for this purpose a correspondingarrangement for the color strips and phase shift of the color selectionvoltage.

The tube is otherwise operated so that the intensity modulation of theelectron beam is connected to the Wehnelt cylinder (signal voltage S inFIG. 5) 'while the modulation of the color selection grid or screenelectrode, respectively, effects the correct color allocation directlysuccessively for the individual picture points. The arrangement would ofcourse operate in particularly simple manner, if the direction of thelines would extend in the longitudinal direction o-f the impact strips.The color selection could then be etfected in particularly simple manner line-wise or partial-picture-wise in the. manner of the so-calledline-skip method; however, in view of the NTSC- method decided upon inthe United States, an approximately similar television standard can beexpected, and the color selection can -be efiected picture-point-wise,that is, simultaneously.

So 'far as the primary electron beam is concerned, there is merely posedthe requirement that it has a diameter, tor example, upon striking theVenetian blind grid, which is not `greater than a picture point, thatis, that it has that value which results from the line number and thepicture size. If the division of the Venetian blind grid is selectedcorresponding to the line and picture point width, so that the beamapproximately just fills the gap opening (gap width), it would bepossible, as already mentioned, that the electron beam records the linein simplest manner in parallel to the metal slat. The beam wouldsimultaneously strike two Venetian blind or impact slats and therebyproduce `a double point, merely in the case of some rasterdiscrepancies, that is, for example, in case the individual line doesnot extend exactly linearly if the line and impact slat form a finiteangle, which however would with correct color selection becomenoticeable upon the screen picture as a regularly occurring structure.This phenomenon is according to the invention eliminated by a kind ofsynchronization, provided for utilizing for always strikes two impactstrips.

the control of the deflection operation the increased number ofsecondary electrons released preponderantly `at the edge of an impactslat facing the cathode, which are also afiected by the intensity of theprimary beam and reach the cylindrical electrode approximatelycompletely. However, other known synchronizing measures may also beemployed for eliminating this phenomenon.

These phenomena can be entirely eliminated by crossing the line and theparallel slat in longitudinal directions at a desired angle, preferablya right angle. Assnming that the line is recorded by uniform advance ofthe electron beam and that the gap width will approximately equal thepicture point width, there will then practically always prevail thecondition that the primary beam enters two gaps simultaneously, that is,that it simultaneously Such a phenomenon of double point tormationcouldbe avoided with intermittent advance of the electron beam, bysuperimposing, for this purpose, on the deflection field, a sawtooth' orsine voltage of suitable frequency, namely, corresponding to the numberof Venetian blind slats, in such a manner,

that the scanning beam, during the time interval of one period of thecolor modulation, strikes only one impact slat. a measure will be thatintervals of nearly constant voltage or very steep voltage increase willalternately be produced, causing an abrupt intermittent advance of theelectron beam. This advance can then be synchronized in suitable manner.This may be efiected, for example, in the previously explained manner,by utilizing that part of the secondary electrons 10 (FIG. 2) which arereleased at the edges facing the cathode and 'are not used for theimaging or picturing. It must be considered in this connection that theopposing field utilized between the electrodes and 4 for the parallelingof the primary beam deflects these secondary electrons, always presentin certain numbers, to' the electrode 4, so that they may be used forsynchronization even with fluctuating intensity of the primary beam.

' This measure can be `avoided and a better resolution can at the sametime be obtained, by making the division of the Venetian blind screenand, of course, correspondingly the elementary groups of the picturescreen, finer, so that the primary beam appears simultaneously, forexample, in at least three gaps, or upon three impact slats. The greaterresolution is efiected due to the fact that the intensity assumes,during the. advance of the primary beam by one picture point width, aclock-wise course with pronounced maximum, for each partial picturepoint formed through a gapior an-impact slat, respectively. The color isthereby always correctly reproduced; only the separation line betweentwo adjacent colors will be somewhat blurred in a width correspondinglysmaller than the width of the picture point. This can be remedied by asimple synchronization of the color selection voltage in a time spacingof about one line. p

FIG. 4 shows part of the grid arrangement with the corresponding beamcourse, for the case that the Venetian blind grid 5 is not struck in itsCapacity as an impact electrode, by electrons with a certain terminalvelocity, for initiating the production of secondary electrons, but thatthe primary beam or better, briefiy, the electron beam, is in theopposing field slowed down or decelerated to a greater extent thanhereinbefore described, by the potentials placed on the Venetian blindgrid and on the cylinder electrode. The electrons of nearly zero voltenergy, which 'are in this manner strongly slowed down are pulleddirectly through the permeating field of the screen electrode, from thepicture space between the metal slats of the Venetian-blind grid 5,which are arranged in the same manner as in FIGS. 2 and 3, withoutthereby striking the slats. FIG. 4 shows the beam course whereby theelectron beam Z is by the opposing field of the cylinder electrode 4 andthe Venetian blind grid 5` strongly slowed down and deflected. The slowelectron beam is In the case of a sine Voltage, the result or" such&041,489

6 in its direction, for example, by the voltage on the color selectiongrid 6 relatively easily infiuenced and is accordingly deflected to thedesired color strip of the screen 7 with the conductive support 8.

' FIG. 5 shows by way of example the circuit conditions provided for the-above described am'angement illustrated in FIG. 4, in which theelectrons are slowed down in the range of the Venetian blind grid toabout 0 volt, that is, without utilizing secondary electrons, theVenetian blind grid 5 being as shown on 0 Voltage. As noted before, thesignal from the source S is connected to the Wehnelt cylinder, the lowvoltage oircuit of S extending from the battery to one terminal of theWehnelt cyl inder having its other terminal connected to 0 voltage. Aslikewise mentioned before, the color selection voltage MS is connectedto the color selection grid in a circuit biased at volts. Thecylindrical electrode 4 is at +200 volt potential, the beam generator 3at +1000 volt potential, and the luminescent screen 7, 8 is at +10000volt potential. These voltage values are given to indicate a typicalexample.

The embodimentaccording to FIG. 6 difiers-from the one shown in FIG. 3merely in the structure of the luminescent electrode 7 and support 8therefor, both forming the screen electrode ofthe arrangement. In FIG.6, the support 8 is' generally slightly sawtooth shaped and carries uponthe respective inclined flanks the elementary groups of color stripsdescribed before.

'Ihe invention is not inherently limited to the illustrated examples andespecially not to picture tubes with the kind of deection shown in FIGS.1 and 5 but is particularly advantageously suited for use in connectionwith fiat-type picture tubes.

The color picture tube according to the invention has the knownadvantages of a single beam tube and the advantages of full intensityutilization of the electron beam due to'the use of the color strips; itis, moreover, technically easily produced and has, as `Compared withheretofore known single beam :color picture tubes, further very decisiveadvantages. It is, inter alia particularly important and advantageousthat no requirements, having to do with color selection, are at allplaced on the primary deflection system, that is, on the deflectonsystem for the electron beam leaving the beam generating system, butthat the deflection system can be constructed as in the case of normalmonochrome picture'tubes, and that no raster discrepancies can result inwrong color selection. Due to the absence of disturbing secondaryelectrons incident to the picturing, a good contrast is obtained withthe described tube and moreover, if desired, an effectivesynchronization is obtained by applying simple control using secondaryelectrons. The color picture tube according to the invention is alsosuitable for television impulse Conversion according to the NTSC-mcthodand therewith automatically applicable for the reproducton of monochromepictures. As compared with the shadow mask tube, the tube according tothe invention has the considerable advantage that the high frequencytelevision impulses or signals (S in FIG. 5) can be connected directlyto the Wehnelt cylinder without requiring subdivision into two or threecolor impulses. In addition, a higher illumination yield 'With respectto the individual colors can be etfected in simple manner by phaseshifting the color selection Voltage and by arranging the colors incorresponding sequence.

Changes may be made within the scope and spirit of the appended claimswhich define what is believed to be new and .desired to have protectedby Letters Patent.

I claim:

1. A single-beam electron beam tube for the reproduction of colortelevision pictures, having focusing and deflection means customary inconnection with monochrome pictures tubes, and having a picture screenconnected to high voltage and carrying luminescent substances disposedthereon in `at least two discrete regularly distributed strips, suchsubstances represent ing elementary groups and becoming responsive toelectron impact luminous in different colors, comprising at least onegrid disposed spaced from the picture screen substantially parallelthereto, electrode means disposed to bend said beam whereby the beampath entering said grid is always substantially perpendicular to theplane of such grid, the latter consisting of narrow metal slats arrangedin the manner of a Venetian blind said metal slats being inclined to thetube axis so as to extend across substantially the entire area traversed by the electron beam, in the mannerof a partially openedVenetian blind, decelerated, and slow readily deflected electronsappearing in the region of the Venetian blind grid, said last mentonedelectrons being by the acceleration field of the screen electrodedeected from their paths and thereby focused so as to efiected byfurther means,

periodically affecting the acceleration thereof successivo focusng ofsaid electrons upon individual color strips of an elementary group ofthe screen allocated respectively to a slot formed by two adjacent metalslats.

2. An electron beam tube according to claim 1, wherein said Venetianblind grid carries approximately cathode potential, whereby theelectrons are slowed down to about volt without striking the slats ofsuch grid.

3. An electron beam tube according to claim l, wherein the slats of saidVenetian blind grid are inclincd by about 45 to the tube axis.

4. An electron beam tube according to claim l, wherein the slats of saidVenetan blind grid are approximately 0.8 millimeter wide.

5. An electron beam tube according to claim 1, wherein the number of theslats of said Venetian blind grid and therewith the number of elementarygroups of the screen electrode are at least equal to the number oflines.

6. An electron beam tube according to claim 1, Wherein a second grid,serving for the color selection, is arranged between the Venetian blindgrid and the screen, spaced from the screen electrode, such second gridbeing made of parallel tensioned' mutually interconnected wireeX-tending in a .plane disposed parallel to the screen, the grid spacing ofsaid wires corresponding approximately to the width of an elementarygroup, 'said wires being thereby disposed in planes which extend throughthe edges of the metal slats of the Venetian blind grid facing thescreen and standing perpendicularly with respect to the screenelectrode, said wires receiving periodically varying deflection voltagecorresponding to a modulaton so as' to elfect a positive bias thereforwith respect to the Venetian blind grid, said defiection voltageconstituting the color selection voltage.

7. An electron beam tube according to claim 1, wheren said screenelectrode receives a color selection voltage which is periodicallyvariable in three stages, whereby the electrons are with increasngimpact energy successively focused upon the color strips of anelementary group, such increase in impact energy being effected inreversed sequence with respect to the luminescent yield of said colorstrips.

8. An electron beam tube according to claim 1, wherein said screen is asubstantially plane screen provided with a transparent and conductivesupport and carries a high potential with respect to said cathode andneighboring electrodes.

9. An electron beam tube according to claim 1, wherein said screen is asubstantially plane screen with strip-like subdivisions exhibiting aslight sawtooth structure, and carrying upon inclincd flanks thereofelementary groups of color strips. 7

10. An electron beam tube according to claim 1, comprising anapproximately cylindrical electrode disposed between said beamgenerating system and said Venetian blind grid, said cylindricalelectrode being dimensioned and provided with a potential so as to slowdown the electron beam which describes a rectangular raster and to focussaid beam and to deflect it for entry thereof parallel to the tube axis,approximately into the plane of said Venetan blind grid.

'11. An electron beam tube according to claim 10, comprisng means foreffecting line synchronization, said means being controlled by secondaryelectrons derived from said cylindrical electrode.

12. An electron beam tube according to claim 1, wherein the width of thenarrow metal slats and twice the mutual spacing therebetween areapproximately equal to one and one-half of the width of an elementarygroup, the pitch of said slats being approximately equal to the width ofthe elementary group.

References Cited in the file of this patent UNITED STATES PATENTSLawrence June 28,

